The present invention relates generally to surgical procedures for spinal stabilization and more specifically to instrumentation adapted for inserting a spinal implant within the intervertebral disc space between adjacent vertebra. More particularly, while aspects of the invention may have other applications, the present invention is especially suited for disc space preparation and implant insertion into a disc space from an anterior surgical approach to the spine.
Various surgical methods have been devised for the implantation of fusion devices into the disc space. Both anterior and posterior surgical approaches have been used for interbody fusions. In 1956, Ralph Cloward developed a method and instrumentation for anterior spinal interbody fusion of the cervical spine. Cloward surgically removed the disc material and placed a tubular drill guide with a large foot plate and prongs over an alignment rod and then embedded the prongs into adjacent vertebrae. The drill guide served to maintain the alignment of the vertebrae and facilitated the reaming out of bone material adjacent the disc space. The reaming process created a bore to accommodate a bone dowel implant. The drill guide was thereafter removed following the reaming process to allow for the passage of the bone dowel which had an outer diameter significantly larger than the reamed bore and the inner diameter of the drill guide. The removal of the drill guide left the dowel insertion phase completely unprotected.
More recent techniques have advanced this concept and have provided further protection for sensitive tissue during disc space preparation and dowel insertion. Such techniques have been applied to an anterior approach to the lumbar spine.
An initial opening or openings are made in the disc space and the height of the disc space is distracted to approximate normal height. Typically, a first distractor is inserted with a height estimated by radiological examination. If additional distraction is required, the first distractor is removed and a second, larger distractor is inserted. However, since the positioning of the distractors is performed without the benefit of protective guide sleeves, the switching of distractors increases the potential for damage to neurovascular structures and may correspondingly increase the time of the procedure.
For bilateral procedures, a double barrel sleeve may be inserted over the distractors, with a central extension extending into the disc space to maintain distraction. One limitation on guide sleeve placement is the amount of neurovascular retraction that must be achieved to place the guide sleeves against the disc space. For some patients, a double barrel sleeve may not be used because there is insufficient space adjacent the disc space to accept the sleeve assembly. Thus, there remains a need for guide sleeves requiring less neurovascular retraction for proper placement and providing greater protection to adjacent tissue.
While the above-described techniques are advances, improvement is still needed to reduce the procedure time by utilization of improved instruments and techniques, to reduce the potential for damage to sensitive tissue adjacent the disc space, and to limit the amount of vessel retraction necessary to utilize the protective instrumentation. The present invention is directed to this need and provides more effective methods and instrumentation for achieving the same.
The present invention relates to methods and instrumentation for vertebral interbody fusion. In one aspect of the invention, the instruments define a reduced width configuration that allows bilateral insertion of cylindrical and tapered implants into the disc space.
In another aspect of the invention, a surgical instrument assembly for distracting a spinal disc space is provided. The assembly includes a first distractor that has a first shaft extending between a proximal end and a distal end and a first distractor tip defining a distraction height that extends from the distal end of the first shaft. The first distractor also has a projection extending from a medial side of the shaft. The assembly further includes a second distractor having a second shaft extending between a proximal end and a distal end and a second distractor tip extending defining a distraction height. The second distractor also has a notch formed in a medial side of the second shaft. The assembly also includes a guide sleeve having a working channel extending between a proximal end and a distal end the sleeve. The first and second distractors are received in the working channel of the guide sleeve with the projection positioned in the notch. The proximal end of the first and second distractors and the guide sleeve are coupled to a distractor driver cap that has a side opening that allows the distractor driver cap to be side-loaded onto the proximal ends of the first and second distractors and the guide sleeve.
In another aspect of the present invention, a method for preparing a spinal disc space between a pair of vertebral endplates for insertion of an implant therebetween is provided. The method includes inserting a guide sleeve to the disc space from an anterior approach, the guide sleeve having a working channel providing access to a first disc space location and a second disc space location; distracting the disc space to a desired disc space height; preparing the first disc space location through the working channel for insertion of a first implant therein; inserting a reamer plug through the working channel into the first disc space location; preparing the second disc space location through the working channel for insertion of a second implant therein after inserting the reamer plug; inserting the second implant through the working channel into the second disc space location, the second implant being tapered to establish a desired lordotic angle between the vertebral endplates; removing the plug from the first disc space location after inserting the second implant; and inserting the first implant through the working channel into the first disc space location, the first implant being tapered to establish a desired lordotic angle between the vertebral endplates.
In a further aspect of the invention, an implant inserter is provided. The implant inserter includes an implant holder engageable to an implant that is biased to the disengaged position. The implant holder is threadingly engaged in the hollow interior of a driver sleeve. The driver sleeve has a plastic bushing on its distal end that contacts a tapered portion of the implant holder to move the implant holder to the engaged position with the implant.
Related objects, advantages, aspects, forms, and features of the present invention will be apparent from the following description.